The present invention relates to a compressor which forms a refrigerating cycle of a refrigerating machine, an air conditioner, or the like and, more particularly, to an improved winding structure of an electric motor unit of a compressor.
A compressor used in, for example, a refrigerating machine and an air conditioner includes a compressing mechanical unit for compressing a refrigerant and an electric motor unit for driving the compressing mechanical unit. The electric motor unit has a stator and a rotor.
The electric motor unit is provided with two- or four-pole three-phase coils in order to save energy and pursue comfort in a refrigerating-cycle operation. It is driven by the power supply of an inverter.
FIGS. 15A and 15B illustrate stators Sa and Sb, respectively. These stators are each obtained by winding a wire M on a stator core K. The core K is constituted of a ring-shaped yoke section y and teeth sections t projected from the inner wall of the yoke section y and arranged at regular intervals. The yoke section y and teeth sections t are formed integrally with each other as one component. It is well-known to call an interval between the teeth sections a slot r.
Taking into consideration the two- or four-pole three-phase coils, the number of slots r is usually 12n (n is a positive integer). The wire M is wound on the core K so as to bridge the slots r by the inserter winding method.
Since, in this winding method, the end of a coil of the wire M, which is projected from each of end faces of the stators Sa and Sb, is raised, with the result that the surface area of the coil is increased and so is the leakage current.
The leakage current is proportionate to both the chopping frequency of the inverter and the surface area of the coil. In particular, the coil end is exposed to a refrigerating machine oil (lubricant) for lubricating the compressing mechanical unit, or a liquid or gas atmosphere mixing a refrigerant and a refrigerating machine oil, which are all conditions for increasing the leakage current.
Since the coil end is large, the circumference of the coil is lengthened, thus increasing in both costs and copper loss of wire resistance. Moreover, the wire is easily damaged when it is wound or the coil end is shaped thereafter.
Recently alternative Freon (chlorofluorocarbon) excluding chlorine has been used in favor of environmental protection. There occurs a new problem in compatibility between the alternative Freon and the refrigerating machine oil supplied into the compressor.
As is apparent from the graph of FIG. 13 showing a variation in oil surface level, the level of the refrigerating machine oil varies with the refrigerant which is to be dissolved into the refrigerating machine oil as operation time elapses. There are many cases where a large amount of refrigerant is present in a sealed case particularly at the beginning of operation.
In the sealed case, the refrigerant and refrigerating machine oil are formed as two layers separated from each other, and the layer of the refrigerating machine oil of low density is formed on that of the refrigerant of high density. Part of the coil end of the lower part of the coil, which is close to the compressing mechanical unit, is soaked into the refrigerating machine oil in which the refrigerant is dissolved.
FIG. 16 illustrates a case 3 of the compressor in order to explain the level of the refrigerating machine oil stored in the case 3. In FIG. 16, reference symbols A, B, C and D indicate oil surfaces of main bearing 12, upper cylinder 11A, lower cylinder 11B and sub-bearing 13, respectively.
Since a large amount of oil stored at the bottom of the case 3 is sucked up into each compression sliding unit by an oil pump immediately after the compressor is started, the oil is greatly reduced. If, however, the operation continues for one or two minutes, the oil circulating in a refrigerating cycle is returned to the compressor and exhaled into the case together with compressed gas; accordingly, the oil surface level is raised and stabilized between oil surfaces A and B.
Even in the steady state after the transition from the start to the normal operation of the compressor, the level of the projected coil end is high and thus part of the coil will be soaked into the refrigerating machine oil.
There is polyglycol oil, ester oil and the like as a refrigerating machine oil which is compatible with the alternative Freon. If, however, the polyglycol oil is selected, the following problem will arise. Since the volume resistivity of polyglycol oil is considerably lower than that of mineral oil which has been used conventionally, the current leaking from the electric motor unit increases greatly and thus electrical insulation deteriorates.
An object of the present invention is to provide a compressor having an electric motor unit capable of reducing in leakage current to secure electrical insulation.
To attain the above object, there is provided a compressor comprising a compressing mechanical unit which inhales a refrigerant excluding chlorine, compresses the refrigerant, exhales a compressed refrigerant, and collects a refrigerating machine oil compatible with the refrigerant, thereby lubricating the compressing mechanical unit with the refrigerating machine oil, and an electric motor unit having a stator and a rotor, for driving the compressing mechanical unit, the stator being constituted by winding a wire on a stator core, wherein the stator core includes a yoke section and teeth sections, and the wire is directly wound on the teeth sections.
According to the present invention, the wire wound around the stator core, especially the coil end is made compact, with the result that the current leaking from the coil end is reduced to improve in electrical insulation.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.